or Shortwave Reception Problems?
We may be able to help......
(without you having to spend a dime)
By Chris Justice
know that this topic has been discussed and written about many times,
but, I think it is important enough that we discuss it again one
more time, from a technical, yet not so technical stand-point.
Good reception is very easy if you have the
right tools... mostly knowledge. I have found through many years
of designing products that it's always easier to fix a problem than
throw a big Band-Aid on it.
Visualization: Looking at just a single
station on the AM broadcast band (below). The green moving triangles
are the signal that is broadcast from the station you are listening
to. The blue line is, obviously the noise, the red line is the bottom
noise floor that your receiver is capable of receiving under the best
of circumstances. Important to note: Noise Floor is
usually expressed as the receiver's maximum sensitivity and can be, and usually is misunderstood. This is
because, if your home or office has too much noise, your sensitive
high-dollar receiver cannot receive down to it's potential noise floor.
You might as well be listening to a 5 dollar pocket radio! Don't get
frustrated with your radio, it's really not it's fault.
The radio noise problem is as old as
radio itself. Unfortunately it is getting worse as technology steadily
progresses and more man-made electronic products hit the shelves.
This is a direct result of mainly consumer products that generate
an increasingly higher noise level. The technology behind the AM
broadcast signal is very out-dated as far as current technology
is concerned, not to mention that the AM broadcast band is located
in the very vulnerable medium wave frequency band.
For instance, looking around the room here I
can spot about 80 different sources of noise. The computer I am
writing this article on and the LCD monitor, those two devices generate
a HUGE amount of noise and would give any regular AM receivers
a very bad time. The dimmer switch for the office lights.... bad
news. Even the low power flourescent lightbulbs I have overhead
cause an extreme problem for any AM reception. Oh, how I wish I
could experience the days before all of the digital consumer products,
dimmer switches, computers, and noisy lighting products, just to
experience what a noise-free AM signal sounded like. Times have
really changed. One possibility to reduce the modern day, man-made
noise is with a high-tech solution. The DSP (Digital Signal Processor).
This is a whole different subject and a little too much to get into
here. You can read a little more about DSP here.
The selection of a quality receiver is important.
But the antenna and listening location is most important. A good
AM or shortwave antenna, in the right location can solve your problem
and make your listening much more pleasant. In addition, a good quality AM Antenna can be used to increase the reception of the signal.
Types of receivers:
Before you go out and purchase a high-dollar
receiver, please take the following statement into consideration.
To some extent, the type of receiver you use will help to eliminate
some of your noise problem. There are many receivers with good IF
filters that can help reduce the noise coming form external sources.
However, in most cases, if you read this article you will already
be knowledgable enough to recognize the source of your noise and
can probably eliminate or reduce it. Again, this is where a directional Tuned AM Antenna, or even an Active AM Antenna will help to possibly eliminate the noise problems because the signal can be tuned directly at the station and away from the point of noise. ... Speaking of noise problems,
let's get to the possible sources.
sources of noise
The following are sources of noise that can
generate headaches, especially on the AM and shortwave broadcast
Dimmer Switches and dimming lamps.
- These will make it almost impossible to receive any type of signal,
regardless of the type of receiver you have or where you are
located. You simply will get nothing but 60 and 120 Hz noise.
Overhead power lines - Especially
with dirty or worn power line insulators. The only way to tell however
is to take a small portable receiver outside and walk around until
you get up to the power pole and the noise is at it's maximum. Hitting
the pole (yes, hitting it) can also tell you a lot. If the noise
crackles or you hear it change, or even go away, this is a good
tell-tale sign that the insulators are dirty. Contact your local
power company if you suspect that source of the noise is coming
from the insulators. They can come out and clean the insulators,
thus eliminating the problem.
Visualization #2: Once you remove the
source of your noise, your receiver's true potential "Sensitivity"
can be recognized. It is then, and only then that you will have the
quality reception that you desire. Note how the receiver's noise floor
is exceptionally lower than in the previous signal on the other page.
This is close to the desired effect you want to achieve. Theortically,
you would like to see the blue line disappear completely, but with
so many man-made noise generators, it is close to impossible. Notice
how the noise floor is at the same level but the noise has been reduced.
- Every fluorescent light has a ballast. A ballast is basically
a transformer that is used to step the voltage up to the requirements
of the fluorescent tube. This can cause a tremendous amount of noise
on any nearby receiver. If you have a specific room that you listen
to the radio in, get rid of all fluorescent lights! If you are really
interested in the best reception possible, get rid of all of the
flourescent lights in your home.
Computers - Yes, I know what
you are thinking. NOT MY COMPUTER, it can't go! Well, it doesn't
have to go, just turn it off when you want to listen to your radio.
Computers are such a huge source of noise that it is almost impossible
to list all of the components that generate noise inside of them.
Now, this is not just limited to the thing in front of you with
the keyboard, many things have computers inside of them. For example
a clock, sprinkler timer, microwave oven (yes, most of them have
computers and do generate noise), cordless phones, especially that
new 900 MHz Spread Spectrum digital phone a lot of you have. I can't
possibly name all of the things which contain computers... heck,
even your radio. The best solution is to minimize them in your listening
room. Oh, did I mention your satellite receiver?
Televisions - Turn it off or
get as far away from it as possible. These things create a huge
amount of noise, especially from the high-voltage transformer inside
of it. If the kids or someone else in the house want to watch the
television you can always take your radio outside or find some type
of quality external antenna to get away from the source of noise.
Motors - Most types of motors
generate or develop a large amount of electromagnetic noise. House
hold motors that shouldn't be overlooked are refrigerators, fans,
inside heater and air-conditioning units, dehumidifiers, bathroom
fans and so on. If it makes noise, sounds like a motor and turns
something, it's causing noise.
Some of these are sources of noise that even
the best, highest dollar receivers and the best antenna systems
in the world cannot overcome and should be momentarily turned off
while listening. If you are an apartment dweller, chances are you
have a neighbor right next door that has a computer or floursecent
light right behind the wall next to you. If this is the unfortunate
situation you are in, try speaking to your neighbor and see if you
can come up with some type of solution. You can always change to
another room. If that doesn't work, you can always purchase a quality
FM Transmitter, place your receiver at the point of least noise
and transmit the signal across your apartment to your radio.....
This is always a possibility and in most cases eliminate your neighbor
problem. As far as noise goes anyways.
Also, a lot of you have hear in the news, mentions
of digital radio on the AM and shortwave broadcast bands. It is
impossible, even for digital radio to get rid of your radio noise.
Digital is a 1s and 0s thing. Basically if you have noise, you get
a Big 0.... nothing at all. Your radio will simply revert back to
analog mode and you will be stuck with enjoying the same high-quality
buzz and hum that you have enjoyed all these years.... (smirk)
So, to summarize, get rid of your noise souce
and get the full potential quality audio from your receiver.
If you have any questions or need some advise,
please feel free to email me.